It shouldn't be a problem, iwht only a few apps
running the overhead is
very small. If by "isn't perfectly tuned" you mean not running SCHED_FIFO
or a patched kernel that its not that supprising, the context switch will
be causing big problems. But, at worst it should just make xruns a bit more
frequent, not go from none to some.
What I have noticed is subtle, I have xruns in both situations but
the rate increases noticeably. I've been running patched kernels but
there are all kinds of parameters
(as I'm sure you know) to tweak before it is sufficiently solid. I
would consider my findings pretty much expected behaviour with a
less then perfectly tuned system.
I thought I'd pipe up here, as I use jack on a totally unpatched, untuned
system (with SCHED_FIFO) and get rock solid performance.